U.S. Pat. No. 3,942,418 discloses a machine permitting the continuous formation of a tubular profile made up of a plurality of bands. This machine comprises a frame having a table traversed by a pivot. A horizontal support can pivot on this pivot to form a certain angle with the longitudinal axis of the machine. On this support there are two rotatable drums connected with one another by a belt. The belt is wound partially around a spindle, one end of which is engaged in the head stock. The two drums are disposed on opposite sides of the spindle. The angular position of these drums, as well as their speed of rotation, is a function of the diameter of the tubular element as well as the thickness of its wall. By reason of the drums being disposed at a certain angular position, the belt describes a helical movement producing on the one hand helical winding of the different bands of paper, metal or other material previously provided with a layer of glue, and, on the other hand, the continuous advance of the tubular element on the spindle. This machine is provided with a multiple cutting device which is displaceable in the direction of the axis of advance of the tubular element, the speed of advance of the cutting device being synchronized with the speed of advance of the tubular element through driving and control means coordinated with the means for forming the tubular element.
From French Pat. No. 2,370,581, there is known a practically identical machine provided with a cut-off device with tubular elements of pasteboard and analagous materials comprising control means actuated by reference marks provided on the tubular element by labels or by the leading edge of the tubular element actuating a translation device of a carriage provided with at least one cutting element of which the speed of advance is regulated by a synchronization assembly. The control means comprise a guide barrel provided with detecting means such as a photoelectric cell which is displaceable along a slot in the barrel by manual control and/or by control through the intermediary of a micromoter.
However, these machines permit the production only of tubular profiles having a round cross-section.
There are also known machines permitting the fabrication of tubular profiles having a square or rectangular cross-section. These profiles are constituted of a plurality of layers of bands of fibrous cellulosic, metallic, or plastic materials. The width of each band is increased as a function of the thickness of the material used. For this purpose, there is known from U.S. Pat. No. 2,256,263 a process and apparatus for the formation of a hollow body of paper.
The process described in this patent consists of continuously feeding a plurality of superposed bands of paper of which the edges are displaced laterally and progressively. Liquid adhesive is applied to the surfaces of the bands to make them adhere to one another. The assembled bands are compressed to form a continuous multiply band having edges which are feathered or tapered in opposite directions while continuing the continuous displacement of the multiply band. The multiply band is progressively fashioned into the form of a tube while the adhesive between the plies is still wet. The edges tapered in opposite directions are abutted to form a continuous tube having a thickness uniform throughout its length. Heat is applied to the tube while it is being displaced longitudinally and maintained in its tubular form to dry the adhesive and to maintain the tubular form. The continuous tube is then cut into lengths of tubular bodies.
Apparatus for carrying out this process comprises a rack in which a plurality of rolls of paper bands are supported. Paper bands traverse a glue machine where adhesive is supplied. This glue machine comprises vats, non-adjustable in height, and the gluing is effected by the single passage of the band over a glue roller without the possibility of applying a coating of glue to opposite sides of each band. For that reason, it is necessary to provide a vat for each band.
The different bands are led toward a press composed of an upper roller and a lower roller. This press assures the assembly of the different bands throughout their widths to form a compact band having multiple plies of which the superposed plies are adhered to one another.
The compact multiply band thus obtained passes to a forming machine comprising an outer forming mandrel and an inner forming mandrel and the compact multiply band gradually modifies its form, that is to say, a flat multiply band is formed into a continuous cylindrical tube. Then, the cylindrical tube is directed into a drying oven comprising sets of upper, lower, and lateral rolls to maintain the tube cylindrical until the adhesive has dried. When the continuous tube leaves the drying oven, it passes into a cut-off machine comprising a circular saw driven by a motor mounted on a carriage displaceable longitudinally at the same speed as that at which the tube is advanced. The circular saw traversing the tube must have a radius greater than the diameter of the tube. For this reason, the diameter of the tube is limited because it is not possible to give the circular saw too great a diameter.
However, it has been observed that during formation of the tube, the outer band is subjected to separating forces while the inner band is crumpled.